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Caramelized Onion Burger

  • Author: Erin
  • Prep Time: 20 minutes
  • Cook Time: 30 minutes
  • Total Time: 50 minutes
  • Yield: 12 sliders 1x
  • Category: Appetizer + Dinner
  • Method: Oven + Stove Top
  • Cuisine: American


Caramelized Onion Burger (or sliders) – the perfect party food that everyone will love! (Paleo/Whole30)



Balsamic Mayo

  • 2 tablespoons mayo
  • 1 teaspoon balsamic vinegar


  • 34 Sunions onions, sliced
  • 1 Tablespoon olive oil
  • 1/2 teaspoon salt
  • 1/2 teaspoon ground black pepper


  • 2 pounds ground beef
  • 2 teaspoons kosher salt
  • 2 teaspoons ground black pepper
  • ghee

Other Toppings: ice berg lettuce (for lettuce buns) bacon and pickles


Balsamic Mayo

  1. Combine ingredients in small bowl and mix to combine.  Make additional sauce as-needed.


  1. Bring large cast iron skillet to medium-high heat. Add olive oil and move it around so that the entire pan is coated.
  2. Add onions and sprinkle with salt and pepper.
  3. Move onions around the pan and bring heat down to medium once onions start to cook down.
  4. Continue cooking onions 15-30 minutes, turning heat down as necessary, until they start to turn golden brown.
  5. Once onions are golden brown, turn off heat and set aside until burgers are ready.


  1. Turn broiler to HIGH and line a baking sheet with foil and place an oven-safe wire rack on top.  Spray the rack with olive oil or other non-stick.
  2. Place ground beef, salt and pepper in medium bowl and mix what hands to combine well.
  3. Divide into 12 equal patties and place on top of wire rack. Ensure the are approximately 1/2 inch thick.
  4. Make a small indent in the middle of each burger and place a small bit of ghee inside.
  5. Sprinkle the tops of the burgers with a little more salt and pepper.
  6. Place in oven on the middle rack and cook for 10 minutes (this will result in a medium-rare center).
  7. Remove and let rest at least 5 minutes.


  1. For a Paleo/Whole30 option serve with a caramelized onions, lettuce bun, bacon, pickle and balsamic mayo.
  2. For a non-Paleo/Whole30 option serve on a slider bun of your choosing, add some cheese and then the caramelized onions, lettuce bun, bacon, pickle and balsamic mayo.
  3. For Whole30/Paleo – double check your ingredients on your balsamic vinegar, mayo, bacon and pickles.
  4. I like to make my own mayo – the recipe is here.


  • You can continue cooking the onions them beyond 30 minutes and they will only continue to caramelize.  I prefer to have my caramelized onions still a little firm and not completely mushy, but that is completely personal preference.
  • You can easily make these into full-sized burger is you prefer.  Simply make 8 burger patties instead of 12.  Make sure you are flattening them enough before cooking.  Cook for 10-12 minutes for medium rare.
  • You can also grill your burgers/sliders if you prefer!

Keywords: caramelized onion burger